# TreeListControlBase.NodeCollapsing event

Occurs before a node is collapsed.

```csharp
public event EventHandler<TreeListNodeAllowEventArgs>? NodeCollapsing;
```

## See Also

* class [TreeListNodeAllowEventArgs](../TreeListNodeAllowEventArgs.md)
* class [TreeListControlBase](../TreeListControlBase.md)
* namespace [Eremex.AvaloniaUI.Controls.TreeList](../index.md)

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